Hydrothermal liquefaction of a wastewater native <i>Chlorella sp</i>. bacteria consortium: biocrude production and characterization

Abstract

Along the recent developments of biofuel production, the hydrothermal liquefaction (HTL) of microalgae appears as a major process step which could take advantage of converting the whole microalgae content instead of only extracting its lipid content. This study presents the HTL conversion of a microalgae Chlorella sp. bacteria consortium using a batch type reactor. The experiments were carried out using a full factorial experimental design approach, where the main chosen factors were the temperature, the residence time at maximum temperature and the dry-matter-to-water ratio. The biocrude oil is the targeted product characterized along this work; its production and its composition were studied. The yields of biocrudes approach other microalgae studies using pure strains of microalgae and batch-type reactors. Maximum yields (37%daf) and lowest O/C ratio (0.167) were obtained at the highest severity conditions (310 °C for 55 min and 0.15 dry-matter-to-water ratio). The energy return on energy invested (EROEI) of the process has been determined. The simulated distillation by thermogravimetric analysis (Sim-Dis-TGA) was conducted on the different obtained biocrude and no significant effect was observed with respect to five evaporation ranges among the studied conditions. GC-MS characterization of biocrude presents the 10 relatively most abundant components for each studied condition.